The present invention relates to a method for producing at least one characteristic line of an air mass detecting device for an internal combustion engine.
Such methods are known in the art. In this method an air mass detecting device on the one hand and an accurate comparison probe on the other hand are installed in an impeller testing stand which must simulate the flow situation in an aspiration region of an internal combustion engine. The signals of both sensors are extracted. From the output signals of the air mass detecting device and from the mass stream detected by the comparison probe, a characteristic line is formed which takes into consideration the influence of the geometry of the aspiration region of the internal combustion engine and its action on the signal.
In normal operation of internal combustion engine the signal of the air mass detecting device serves, in addition to other criteria, for determination of the loading condition of the internal combustion engine. Conventionally, a hot film air quantity sensor is used as the air mass detecting device, which is identified as “HFM-sensor”.
The characteristic line determined by the testing stand research is identified as a “static” characteristic line, since it is produced at static or stationary flow conditions. It is provided in a control device of the internal combustion engine. The problem is however that in many internal combustion engines the airflow in the aspiration region is not stationary, but instead has a pulsed pattern. The correct detection of such a pulsing air flow in real use is difficult for conventional air mass detecting devices in principle, so that a faulty indication is produced which is a function of the frequency and the amplitude of the flow pulsations.
When however the air mass screen determined by the air mass detecting device does not correspond to the actual air mass stream in the combustion chamber of an internal combustion engine, deviations of the emission behavior of the internal combustion engine from an optimal emission behavior can take place.